Mineral fiber insulation is well known and has been a commercial product for a long period of time. The insulation is made from rock or slag fibers often referred to as mineral wool or rockwool.
Research has established that asbestos fibers when inhaled can cause significant disease in man. Though the exact mechanisms responsible for the biological activity of inhaled asbestos fibers is unknown, it is widely believed that their ability to remain in the lung for extended periods of time is an important factor. Mineral fibers have not been linked to disease in man. Additionally, their durability or residence time in the lung appears much less than asbestos fibers.
As an added precaution, however, the German government has proposed regulations for mineral fibers. Mineral fiber compositions meeting the regulations are considered to be free of suspicion. The problem, however, for the manufacturer is to produce fibers which meet the regulations and standard criteria. These fibers must meet the proposed regulations, be fiberizable in standard rockwool processes, have sufficient durability and have acceptable insulating properties.
An important use of mineral fiber insulation is as a fire barrier in buildings. To perform properly in this application, the mineral fiber must have a high temperature resistance. Most mineral wools with a high temperature resistance contain high mounts of iron oxides (4 to 12 weight percent). The iron oxide acts as a nucleating agent so that the fiber will crystallize rather than melt during a fire. This high amount of iron oxide also reduces the high temperature viscosity of the melt and can make fiber forming difficult. This is particularly true for compositions formulated with very high mounts of CaO+MgO to give a high biosolubility.